ionic liquids for enzymatic sensing - doras - dcudoras.dcu.ie/16873/1/acs_meeting.pdf · ionic...

UNIVERSITY COLLEGE DUBLIN � DUBLIN CITY UNIVERSITY � TYNDALL NATIONAL INSTITUTE

29/03/12

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Ionic Liquids For Enzymatic Sensing

Monday, 2 April 12


29/03/12

1 of 33

@ cyrusmekon #ACS

Ionic Liquids For Enzymatic Sensing

Monday, 2 April 12


Contents The need for wearable sensors.

Wearable electrochemical sensors.

Diverse material for sensing platforms.

Electrochemical biosensing: The road ahead.

Conclusions.

• Ionic Liquids & Organic Electrochemical Transistors (OECTs)

• Ionogels & OECTs

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CLARITY – SFI CSET

• 5-year, €16.4 million research program to develop next generation Sensor Web Technologies with significant environmental focus

• Brings together fundamental materials science, functional polymers, device prototyping, energy management, adaptive middleware, wearable sensors, distributed environmental monitoring.

www.clarity-centre.org/

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http://www.clarity-centre.org

http://www.clarity-centre.org


CLARITY – SFI CSET

• 5-year, €16.4 million research program to develop next generation Sensor Web Technologies with significant environmental focus

• Brings together fundamental materials science, functional polymers, device prototyping, energy management, adaptive middleware, wearable sensors, distributed environmental monitoring.

www.clarity-centre.org/

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http://www.slideshare.net/hewlettpackard/hp-cense-sensor-networks-and-the-pulse-of-the-planet

The need for sensors.

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HP's Peter Hartwell: "one trillion nanoscale sensors and actuators will need the equivalent of 1000 internets: the next huge demand

for computing!"


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Sensing Systems: $ 70 B global market by 2013 (Frost & Sullivan)

Sensing Services: $290 B Global market by 2013 (Harbour research)

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Similar strategies proposed by IBM, INTEL, Nokia….

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In-house UV Sensor

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2 hrs Sicily

Dublin

In-house UV Sensor

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The need for wearable sensors.

• Wearable sensors allow the continuous monitoring of a person’s physiology in a natural setting.

• Health-monitoring systems using electronic textiles are mainly targeting applications based upon physiological parameter measurements, such as body movements or electrocardiography (ECG).

• However, due to their relative complexity, there is very little activity in the development of real-time wearable chemo/bio sensing for sports applications.

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PHYSICAL SENSORSBreath rate, heart rate, activity, posture, skin temperature…

Current Wearable Sensors

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TRAINTRAK™heart rate, respiration rate, posture,

activity, and GPS location

NIKE-APPLE iPOD SPORTS KIT

PHYSICAL SENSORSBreath rate, heart rate, activity, posture, skin temperature…

LIFESHIRT®

Bipolar affective disorder

and schizophrenia‘Activity’


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The myTREK utilizes two LEDs combined with a photo sensor to detect minute changes in the user's blood pressure to accurately measure pulse. A built-in accelerometer allows the myTREK to adjust for movement during exercise from the user's heartbeat allowing for an extremely accurate measurement of pulse and calories burned.

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Ultra-thin, self-adhesive electronics

device that can effectively measure

data about the human heart, brain

waves and muscle activity--all

without the use of bulky equipment,

conductive fluids or glues.

John Rogers @ University of Illinois

11/08/2011

Link :http://www.nsf.gov/news/news_summ.jsp?cntn_id=121343&org=NSF&from=news

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http://www.nsf.gov/news/news_summ.jsp?cntn_id=121343&org=NSF&from=news

http://www.nsf.gov/news/news_summ.jsp?cntn_id=121343&org=NSF&from=news



PharmChek Sweat Patch Abbot Freestyle Navigator

Glucowatch NASA: Wearable sensor patches

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PharmChek Sweat Patch Abbot Freestyle Navigator

Glucowatch NASA: Wearable sensor patches

SAMPLING BIG ISSUE!!!!h3p://www.youtube.com/watch?v=pmMo3AYKOk0

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http://www.youtube.com/watch?v=pmMo3AYKOk0

http://www.youtube.com/watch?v=pmMo3AYKOk0

Ideas Tree for Ionic liquids

StableNon-

volatileOrganic

Salts

ActiveStableSolar C

ells

Media

Electrolytes

Reactiv

e

Catalytic

Bioactive

Medicinal

Act

ives

Agrichem

Fungi

Cryo-Biostabilization

Bio-Engineering

Cells

Proteins

VolatilePlastic

Electrowinning

Batteries

Electrosynthesis

Ti, AlI2

Mg

Li

Bio

TiO2

Doped

Organic

Solvents

Sepa

ratio

ns

Nanostructured

H+

Li

Uns

tabl

e

Biocidal

MIC

Antibacterial

Cell bioprocessing

2010 2005 2000 1995 2000 2005 2010

http://www.chem.monash.edu.au/ionicliquids/Monday, 2 April 12

Ideas Tree for Ionic liquids

StableNon-

volatileOrganic

Salts

ActiveStable

Media

Electrolytes

Reactiv

e

Catalytic

Bioactive

Medicinal

Act

ives

Agrichem

Fungi

Cryo-Biostabilization

Bio-Engineering

Cells

Proteins

Volatile

Plastic

Electrowinning

Solvents

Sepa

ratio

ns

Uns

tabl

e

Biocidal

MIC

Antibacterial

Cell bioprocessing

2010 2005 2000 1995 2000 2005 2010http://www.chem.monash.edu.au/ionicliquids/Monday, 2 April 12


Ionic Liquids: A brief introduction

[1] H. Zhao, J. Chem. Tech. Biotech, 2010, 85, 891-907.

• Ionic liquids (ILs) have evolved as a new type of non-aqueous solvents for biocatalysis, mainly due to their unique and tunable physical properties [1]

IL polarity Hydrogen bonding bascicity

Ion kosmotropicity

Viscosity

Enzyme dissolution

Factors that affect Enzyme activity in ILs

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[2] K. Fujita, D. R. MacFarlane and M. Forsyth, Chem. Commun., 2005, 4804-4806.

PBS

Through smart design enzyme stability can be greatly enhanced

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[2] K. Fujita, D. R. MacFarlane and M. Forsyth, Chem. Commun., 2005, 4804-4806.

Through smart design enzyme stability can be greatly enhanced

• Choline DHP showed enzyme stability up to 130 oC [2]

• Enhanced solubility of cytochrome c.

• dhp anion provided both a proton activity similar to that in neutral water as well as hydrogen bonding donor and acceptor sites.

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Sensing Platform: Ionic liquids

• Point-of-care (POC) glucose biosensors play an important role in themanagement of blood sugar levels in patients with diabetes.

• One of the most commonly used enzymes in glucose biosensors isGlucose Oxidase (GOx).

• Amperometric biosensors employing IL’s have been reported previously,for example, ([C4mIm][BF4]) has been used as a mediator in a electrochemicalH2O2 biosensor[3].

[3] Y. Liu, M. Wang, J. Li, Z. Li, P. He, H. Liu and J. Li, Chem. Commun., 2005, 1778-1780.

• This interest is driven by the need to find molecular environments in whichenzymes are highly stabilized while retaining redox activity.

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Organic Electrochemical Transistors (OECTs)

Sensing Platform: OECTs

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• The field of organic electronics has grown significantly in the past 20 years largely due to the many desirable properties of organic semiconductors such as low cost, ease of processing and tunability through synthetic chemistry.

• A prototypical semiconductor used in OECTs is poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS), a material that is commercially available and stable under a variety of conditions.

• PEDOT:PSS is a degenerately doped p-type semiconductor (commonly referred to as a conducting polymer), where holes on the PEDOT are compensated by acceptors (SO3–) on the PSS.

• OECTs have been utilized in a variety of biosensing applications such as thedetection of metabolites, ions, neurotransmitters, cells, antibodies and DNA

[4] D. Bernards, G. Malliaras, “steady state and transient response of organic electrochemical transistors” Adv. Func Mat 2007.

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Ion-‐to-‐electron converter

Vd

-+ + + + +- -- -

+-+ +

++- --

-



The organic electrochemical transistor [4]

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Vd

-- -- -+

-

+

+

+

+

- -- -

+ +

Vg



The organic electrochemical transistor [4]

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• Response of the transistor is defined as the difference in modulationlevel of the drain channel during application of a gate voltage in theabsence and presence of a target analyte

• To develop an enzymatic sensor based on an OECT that uses an IL as an integral part of its structure.

The Aim:

• The strategy involves patterning the RTIL over the active area of the OECT, and using it as a reservoir for the enzyme and the mediator.

• GOx enzyme for glucose detection.

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• Important properties of the electrolyte for this device must include wetting the PEDOT : PSS film.

[5] S. Y. Yang, F. Cicoira, R. Byrne, F. Benito-Lopez, D. Diamond, R. A. Owens and G. G. Malliaras, Chem. Commun., 2010, 46, 7972-7974.

Sensing Platform: Ionic liquids & OECTs

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• Important properties of the electrolyte for this device must include wetting the PEDOT : PSS film.

• This allows the enzyme and the mediator to be patterned over the active area of the device.

• The IL should be miscible with the aqueous phase (PBS).

• Triisobutyl(methyl)phosphonium Tosylate ([P1,4,4,4][Tos]) due to the hydrophilic nature of the cation / anion.

Fig 1: [P1,4,4,4][Tos] Ionic Liquid used in this study. (provided by Cytec Canada Inc. Ontario, Canada)

P

CH3

C4H9C4H9

C4H9

S

O

O

O



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• The transient response of the drain current of an OECT upon application of a gate voltage of 0.4 V and duration of 3 min. Thedrain voltage was -0.2 V.


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• Inset shows the concept of device operation, and the arrows indicate thedissolution of the RTIL carrying the enzyme and the mediator into the analytesolution.

• Current modulation of the OECT as a function of glucose concentration.


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• The data show the characteristic decrease of drain current upon gatingwhich has been understood on the basis of the reactions shown below

Reactions at the gate electrode (a) and at the channel (b) of the OECT.


D-glucono-1,5-lactone GOxred Fe+ PEDOT+ : PSS- + e-

D-glucose GOx Fe PEDOT+ : PSS-

(A)

(B) PEDOT+ : PSS- + M+ + e- PEDOT + M+: PSS- } Drain Electrode

}Gate Electrode

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Sensing Platform: Ionic liquids & OECTsD-glucono-1,5-lactone GOxred Fe+ PEDOT+ : PSS- + e-

D-glucose GOx Fe PEDOT+ : PSS-

(A)

(B) PEDOT+ : PSS- + M+ + e- PEDOT + M+: PSS- } Drain Electrode

}Gate Electrode

• For example, for 10-2 M of glucose, this cascade of reactions causesa current of 8x10-8 A to flow to the gate electrode.

• As glucose in the solution is oxidised, the enzyme (GOx) itself isreduced, and cycles back with the help of the Fc/ferricenium ion (Fc+)couple, which shuttles electrons to the gate electrode (A).

•At the same time, cations from the solution (M+) enter the PEDOT : PSS channel and dedope it. (B)

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Conclusions:

• Successful integration of an OECT with an IL as electrolyte.


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Conclusions:

• Successful integration of an OECT with an IL as electrolyte.

• The ionic liquid was confined on the surface of the transistorusing a photolithographically patterned hydrophobic monolayer.

• Using the glucose/ glucose oxidase pair as a model, it wasdemonstrated the analyte detection in the 10-7 to 10-2 M concentrationrange.

• The enzyme was in a dispersed state in the ionic liquid, which mayprove to be a good strategy for improving long-term storage.


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• Currently for applications in materials science, there is a growing interest in ‘ionogels’.

• • Polymers with ionic liquids integrated such that they retain their specific properties within the polymer/gel environment.

Electrochemical biosensing: The road ahead

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[6] M.-A. Nouze, J. L. Bideau, P. Gaveau, S. Bellayer and A. Vioux, Chem. Mater., 2006, 18, 3931-3936.


Ionogel synthesis:

Inorganic route: Oxides, Sol-Gel.

• Applications in catalysis & photonics.

[6]

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Ionogel synthesis:

Inorganic route: Oxides, Sol-Gel.

• Applications in catalysis & photonics.

[7] T. Ueki and M. Watanabe, Macromolecules, 2008, 41, 3739-3749.

Organic route: Polymers, Acrylamide gels

• Applications in solid state electrolytes and separations

[6]

[7]

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Ionogel synthesis:

[7] T. Ueki and M. Watanabe, Macromolecules, 2008, 41, 3739-3749.

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Ionogel synthesis: Organic route

Monomer

Crosslinker Ionic liquid

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Ionogel synthesis: Organic route

Tea leaves

MilkWater

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Ionogels: Ones we prepared earlier

Sweat Sensing

1-‐ BROMOPHENOL BLUE2-‐ BROMOCRESOL GREEN3-‐ BROMOCRESOL PURPLE4-‐ BROMOTHYMOL BLUE

pH

3.8 5.4

5.2 6.8

6.0 7.6

3.0 4.6

Characteristics:

- Ionogel/dyes

- Image data analysis - Absorbent = passive pump

- Electronics is not required

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Sweat Sensing

[P4,4,4,4][dca]


pH

3.8 5.4

5.2 6.8

6.0 7.6

3.0 4.6

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Sweat Sensing


pH

3.8 5.4

5.2 6.8

6.0 7.6

3.0 4.6

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Sweat Sensing

pH 3 pH 4 pH 5 pH 6

pH 10pH 9pH 8pH 7

Hue“the degree to which a stimulus can be described”

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Electrochemical biosensing: Lactate

• Detection of lactate (deprotonated form of lactic acid) in blood provides abiochemical indicator of anaerobic metabolism in patients with circulatoryfailure. [8]

• Lactate also found in sweat (concentration range between 9 - 23 mM) [9]

Current detection methods

• Lactate concentration increases during physical exercise.

Electro-chemiluminescent

Commercially available : SCOUT (sensilab) system

Carbon nanotubes

[8] M. H. Weil and A. A. Afifi, Circulation, 41, 989-1001 (1970).

[9] J. M. Green, R. C. Pritchett, T. R. Crews, J. R. McLester and D. C. Tucker, European Journal of Applied Physiology, 91, 1-6 (2004).

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• Hydrophilic IL chosen due to miscibility with water.

• Avoid mixing problems with PBS & analyte solution.

• Mix the RTIL (17 % water) and PBS solution containing LOx enzyme ratio 4:1

• Hydrated Il completely dissolved the protein with no precipitation observed

• 20 uL final solution drop cast over OECT

• UV polymerised for 1 min

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• Apply -0.3 V across the Channel

• Trigger the gate electrode at 0.4 V (3 min square wave pulses)

• Introduce 20 uL of PBS solution with desired lactate concentration



Vd

-+ + + + +- -- -

+-+ +

++- ---

+ +

Vg

- 0.3 V

0.4 VIonogel matrix

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• Lactic acid is oxidised to pyruvate and cycles back by the Ferriconium ionwhich carries electrons to the gate electrode

• This leads to a decrease in the potential across the gate / ionogel interface andan increase of the potential at the channel / ionogel interface

As a result more cations from the solution enter the dedoped channel and themodulation of the drain current in response to a voltage increases.

}Gate Electrode

} Drain Electrode

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[10] D. Khodagholy, V. F. Curto, K. J. Fraser, M. Gurfinkel, R. Byrne, D. Diamond, G. G. Malliaras, F. Benito-Lopez and R. M. Owens,J. Mater. Chem., 22, 4440 (2012).

• Modulation in the drain current is much larger than the gate100 nA of current at gate - 11 uA at the Drain

• 10 mins for steady state to be reached after analyte added (diffusion inhibited)

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[10] D. Khodagholy, V. F. Curto, K. J. Fraser, M. Gurfinkel, R. Byrne, D. Diamond, G. G. Malliaras, F. Benito-Lopez and R. M. Owens,J. Mater. Chem., 22, 4440 (2012).

• Response from 10 mM - 100 mM• In concentration range of sweat

• Compatible with detection of lactatein blood (1.3 - 24 mM)

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• Detection of lactate in a relevant physiological range (10 - 100 mM)

• Novelty lies in the configuration of the sensor

- Implications for the wearability of the sensor

• Solid State electrolyte on a flexible transistor based biosensor.

Conclusions

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• Incorporate printable formulations onto OECTs for biosensing

Prin'ng Ionogel

~ 625 nl

2 mm

6 mm

150 um thickness

So whats next?

• Biocompatible Ionogels: pH buffered gels for improved enzymatic shelf life.

• Enzyme stability and reliability of the system needs to be establish

• Incorporate OECT / Ionogel into a wireless communicated microfluidic device.

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Acknowledgments

Vincenzo F. Curto

Prof Dermot DiamondProf George Malliaras

Prof Róisín Owens

Dion Khodagholy

Dr Fernando Benito-Lopez

Dr Robert Byrne

Dr Fabio Cicoira

Dr Sang Yoon Yang

Prof Doug MacFarlaneDr^2 Vijay Ranganathan

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Acknowledgments

Vincenzo F. Curto

Prof Dermot DiamondProf George Malliaras

Prof Róisín Owens

Dion Khodagholy

Dr Fernando Benito-Lopez

Dr Robert Byrne

Dr Fabio Cicoira

Dr Sang Yoon Yang

Prof Doug MacFarlaneDr^2 Vijay Ranganathan

Funding Agencies

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CLARITY Centre & EcosystemINDUSTRY COLLABORATORS

SOCIAL/AGENCY COLLABORATORS

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Thanks for your attention

QUESTIONS?Presentation available for download (@Cyrusmekon)

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http://tinyurl.com/7pk4gnb

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ionic liquids for enzymatic sensing - doras - dcudoras.dcu.ie/16873/1/acs_meeting.pdf · ionic...

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